The invention relates generally to a method of and an arrangement for evaluating a series of originals prior to copying.
More particularly, the invention relates to a method of and an arrangement for determining the definition of a series of originals prior to copying. Such a series of originals may, for example, constitute discrete frames on a strip of film.
In a known method of evaluating a strip of film prior to copying, the transparencies of neighboring regions of the originals or frames are photoelectrically determined. The sizes of these regions correspond to the resolution of the film. The transparency values are processed to generate differential values which are a function of the transparency differences of adjacent regions. The differential values are compared with reference values. The number and/or magnitudes of the differential values which exceed the reference values are evaluated to obtain an indication of the definition of each original.
The German Offenlegungsschrift No. 2 244 340 which corresponds to U.S. Pat. No. 3,981,579, discloses a copier for copying rolls of film. An inspection station for determining the definition of the originals is located upstream of the copying station. The originals or negatives are photoelectrically scanned in the inspection station in order to determine whether or not they are worth copying. If an original is found to be acceptable for copying, it is transported into the copying station and copied. On the other hand, originals which are found to lack sufficient definition for copying are transported through the copying station without being copied.
Only films having marks such as notches or perforations for indicating the locations of the originals can be processed in the above copier. Certain film manufacturers provide these marks on the unexposed film and the marks are than used to properly position the frames or originals in a camera during exposure. Marks of this type are not provided on 135 mm. film, that is, the so-called miniature film. Accordingly, the film must be provided with marks after development in order that it may be copied in the above copier.
A method of marking an exposed film is taught in the German Pat. No. 1 285 317 corresponding to U.S. Pat. No. 3,469,480. This patent makes use of the fact that a detectable change in transparency usually occurs at the boundary of a film frame. The frames are photoelectrically scanned and the transparency values obtained in this manner are used to locate the boundaries of the film frames and hence the film frames themselves. The edges of the film are then provided with notches which identify the locations of the film frames.
U.S. Pat. No. 4,167,678 recognizes that it is not always possible to photoelectrically detect the boundaries of overexposed or underexposed film frames. The U.S. patent thus proposes to photoelectrically detect opposed boundaries of at least one film frame where appreciable changes in transparency occur at the boundaries. The length of the frame is determined from the results of the photoelectric scan and is used as a yardstick to identify the locations of film frames where the boundaries cannot be detected photoelectrically. This makes it possible to provide the film with notches even for those frames which do not lend themselves to photoelectric detection.
In both the German patent and the last-mentioned U.S. patent, a separate arrangement as well as an additional operation are required in order to photoelectrically detect the film frames and to provide the film with corresponding notches.